The invention relates to the therapeutic modulation of inflammatory response modulation, and in particular to the suppression of macrophage proinflammatory responses to infectious and/or inflammatory stimuli.
Macrophages are prodigious secretory cells which can produce a number of molecules which can either potentiate or dampen immune responses (Nathan, J. Clin. Invest. 79:319-322, 1987). In response to infectious or inflammatory stimuli, macrophages can produce several proinflammatory molecules, including TNFxcex1, IL-1, IL-6 and IL-12 (Nathan, J. Clin. Invest. 79:319-322, 1987; Trinchieri et al., J. Leukocyte Biol. 59:505-511, 1996). These proinflammatory molecules are important for host defense, because experimentally infected animals deficient in these cytokines are invariably more susceptible to acute bacterial infections than are normal animals (Dalrymple et al., Infect. Immun. 63:2262-2268, 1995; Kincy-Cain et al., Infect. Immun. 64:1437-1440, 1996).
IL-12 is a 70 kDa heterodimer consisting of two covalently linked polypeptide chains, one of 35 kDa (p35) and the other of 40 kDa (p40). IL-12 plays an important role in the development of TH1-type immune responses (Trinchieri et al., J. Leukocyte Biol. 59:505-511, 1996). This cytokine is a potent inducer of IFNxcex3 from T and NK cells, and it has been shown to play a crucial role in the development of immunity to intracellular pathogens (Heinzel et al., J. Exp. Med. 177:1505-1512, 1993; Tripp et al., Proc. Nat. Acad. Sci. USA 90:3725-3729, 1993).
IL-12 is a potent inducer of cell-mediated immune responses, and animals lacking IL-12 are invariably more susceptible to infections with intracellular pathogens (Mattner et al., Eur. J. Immunol. 26:1553-1559, 1996). It has been recently demonstrated that some microbes can influence IL-12 production by macrophages. Leishmania major, measles virus, and HIV have all been shown to downregulate the production of IL-12 by macrophages or monocytes infected with them (Carrera et al., J. Exp. Med. 183:515-526, 1996; Karp et al., Science 273:228-231, 1996; Chehimi et al., J. Exp. Med. 179:1361-1366, 1994). This downmodulation of IL-12 has the potential of providing these pathogens with a means of suppressing the development of cell-mediated immunity.
The production of proinflammatory cytokines such as IL-12, however, must be tightly regulated, since their production is also correlated with many of the pathologies associated with acute sepsis or with autoimmune diseases. The overproduction of IL-12 during an immune response, however, has the potential to be detrimental to the host. IL-12 produced during endotoxemia (Wysocka et al., Eur. J. Immunol. 25:672-676, 1995), and during a number of autoimmune disorders, including insulin-dependent diabetes mellitus (Trembleau et al., J. Exp. Med. 181:817-821, 1995), experimental allergic encephalomyelitis (Leonard et al., J. Exp. Med. 181:381-386, 1995), or collagen-induced arthritis (Germann et al., Proc. Natl. Acad Sci. USA 92:4823-4827, 1995), can lead to exacerbated disease.
In many instances, macrophages can participate in the regulation of proinflammatory cytokines by the production of anti-inflammatory molecules. The secretion of prostaglandins, TGFxcex2, and IL-10 by macrophages has been associated with anti-inflammatory responses (Tsunawaki et al., Nature 334:260-262, 1988; Bogdan et al., J. Exp. Med. 174:1549-1555, 1991; Kunkel et al., J. Biol. Chem. 263:5380-5384, 1988). These anti-inflammatory molecules have the potential to ameliorate the potentially deleterious effects of an overly aggressive immune response. Thus, the balance between the secretion of pro- and anti-inflammatory molecules by macrophages is a critical component of the acute phase response and has the potential to affect the adaptive immune response that subsequently develops.
Interleukin-10 (IL-10) is an 18 kDa cytokine produced by the TH2 subset of CD4+ helper cells. It is also produced by some activated B cells, by some TH1 cells (in humans), by activated macrophages, and by some non-lymphocytic cell types (e.g., keratinocytes). In contrast to IL-12, IL-10 has been associated with an inhibition of TH1-type immune responses. IL-10 has been shown to inhibit the production of TH1 cytokines and the proliferation of TH1 cells to antigen (Malefyt et al., J. Exp. Med. 174:915-924, 1991; Fiorentino et al., J. Immunol. 146:3444-3451, 1991). IL-10 inhibits IL-12 production by macrophages (D""Andrea et al., J. Exp. Med. 178:1041-1048, 1993), and the administration of exogenous IL-10 can diminish the toxicity of LPS (Howard et al., J. Exp. Med. 177:1205-1208, 1993; Berg et al., J. Clin. Invest. 96:2339-2347, 1995). IL-10 has been considered for the treatment of autoimmune diseases such as arthritis (Hart et al., Immunology 84:536-542, 1995) and colitis (Davidson et al., J. Exp. Med. 184:241-251, 1996).
The Fcxcex3 receptor (Fcxcex3R) is a receptor for the Fc region of IgG. B and T lymphocytes, natural killer cells, polymorphonuclear leukocytes, mononuclear phagocytes, and platelets contain Fcxcex3 receptor. The three types of Fcxcex3 receptors include Fcxcex3RI (CD64), Fcxcex3RII (CD32) and Fcxcex3RIII (CD16). CD16, the Fcxcex3RIII, is the prototypical proinflammatory Fc receptor. Ligating Fcxcex3RIII has been associated with the production of proinflammatory cytokines (Cassatella et al., J. Exp. Med. 169:549-567, 1989), and mice lacking Fcxcex3RIII undergo diminished Arthus reactions (Hazenbos et al., Immunity 5:181-188, 1996). CD32, the Fcxcex3RII, is a negative regulator of immune complex-triggered immune responses, and mice lacking Fcxcex3RII have augmented anaphylactic responses to IgG (Takai et al., Nature 379:346-349, 1996). Fcxcex3RI represents a high-affinity receptor found on mononuclear phagocytes. In humans, its binds IgG1 and IgG3. Fcxcex3RII and Fcxcex3RIII are low-affinity IgG receptors.
A mechanism whereby receptor ligation can downmodulate IL-12 production by macrophages has been described (Sutterwala et al., J. Exp. Med. 185:1977-1985 (1997). However, this previously described mechanism of IL-12 downregulation did not exhibit specificity with regard to the macrophage phagocytic receptors that could induce this downmodulation.
Lipopolysaccharide endotoxin (LPS) is a complex macromolecule from the cell walls of certain bacteria, some of which cause diseases like typhoid fever, dysentery, and urinary tract infections and from other bacteria which are common inhabitants of animal and human intestinal tracts but ordinarily do not cause disease. All of these bacteria have in common the same type of cell wall and are classified as Gram-negative. LPS induces the production and release of immunologically active cytokines and other mediators of the proinflammatory response.
There are many pathophysiological effects of LPS, one of which is endotoxemia or septic shock which results from large amounts of endotoxin in the blood. The majority of the cases of septic shock are a consequence of Gram-negative bacteremia (bacteria in the blood). However, the septic shock syndrome can be induced by other organisms including Gram-positive bacteria and fungi. A key factor in the development of toxic shock is the release of LPS from Gram-negative bacteria and the subsequent effects of the endotoxin on various cells in the body which become highly activated. As a result, the host is overwhelmed with many cell substances that lead to circulatory failure, shock and death.
There is a need for a therapeutic modality which is capable of reversing the proinflammatory responses of macrophages to stimuli such as bacteria and bacterial products, and stimuli associated with autoimmune disease. There is needed a therapeutic modality which is capable of inhibiting host proinflammatory immune responses while at the same time inducing host anti-inflammatory responses. In particular what is needed is a modality for dampening the acute response to inflammatory stimuli, such as LPS or Gram-negative bacteria. Such therapeutic modalities would be useful in treating various proinflammatory diseases such as autoimmune disorders and bacteremia caused by gram-negative bacilli.
A method for enhancing IL-10 production by Fcxcex3RI receptor-expressing cells of a mammal is provided. An agent is administered to the mammal, which agent either alone or in combination with one or more substances in the body of the mammal, causes ligation of the Fcxcex3RI receptors on those Fcxcex3RI receptor-expressing cells. The mammal may be a human being. The cells most particularly comprise macrophages.
According to one embodiment, the administered agent is a ligating agent comprising a multivalent antibody which binds to the Fcxcex3RI receptor.
According to another embodiment, the ligating agent comprises an immune complex containing at least two antibody molecules or fragments thereof which contain the Fc region of IgG.
According to yet another embodiment of the invention, the ligating agent comprises an antibody multimer containing at least two antibody molecules or fragments thereof which contain the Fc region of IgG. Preferably, the ligating agent comprises a preparation of IgG comprising IgG dimers, trimers or a mixture thereof. The IgG content of the preparation preferably comprises, on a weight percent basis, at least about 50% IgG dimers, trimers, or a mixture thereof.
A method of inhibiting a proinflammatory immune response in a mammal is provided comprising administering an effective amount of the ligating agent to the mammal to cause ligation of Fcxcex3RI receptors on cells of the mammal.
According to another embodiment of the invention, a method of inhibiting a proinflammatory immune response in a mammal is provided. An IgG antibody is administered, which binds to antigen in the mammal to form an immune complex capable of ligating Fcxcex3RI receptors present on host cells.
According to another embodiment of the invention, a method for treating or preventing shock associated with bacterial endotoxemia, or for treating an autoimmune disorder, is provided. An effective amount of a ligating agent is administered to a mammal in need of such treatment. The ligating agent causes ligation of Fcxcex3RI receptors on cells of the mammal.
According to another embodiment of the invention, a method is provided for treating or preventing shock associated with bacterial endotoxemia in a mammalian host. An IgG antibody is administered, which binds to antigen in the host to form an immune complex capable of ligating Fcxcex3RI receptors present on host cells.
According to another embodiment of the invention, a method for treating an autoimmune disorder in a mammalian host is provided, comprising administering an IgG antibody which binds to antigen in the host to form an immune complex capable of ligating Fcxcex3RI receptors present on host cells.